Determines how many grow lights are needed for any indoor garden area based on total square footage, individual light wattage, and plant light requirements (30W/sq ft for herbs to 75W/sq ft for flowering).
Calculate how many grow lights you need for your indoor garden area.
The grow light coverage calculator determines how many grow lights you need for your indoor garden based on growing area, light wattage, and plant type. Low-light herbs need ~30W/sq ft while flowering plants need ~75W/sq ft.
| Plant Type | W per sq ft | Examples |
|---|---|---|
| Low light | 25–30 | Herbs, lettuce, spinach |
| Medium (vegging) | 40–50 | Tomato seedlings, peppers (veg stage) |
| High (flowering) | 60–75 | Tomatoes, peppers, cannabis (flower) |
Modern full-spectrum LEDs produce about 2–3 µmol/J (photosynthetic photon flux), roughly 40–60% more efficient than HPS (high-pressure sodium) lights. When using LEDs, you can use about 60% of the wattage listed for HPS-equivalent coverage.
30W/sq ft for herbs and greens, 50W/sq ft for vegetative growth, and 75W/sq ft for flowering. These are actual wall-draw watts, not "equivalent" marketing watts.
LED panels: 12–18 inches above canopy for flowering, 24–36 inches for seedlings. Too close causes light burn; too far reduces intensity. Adjust based on manufacturer recommendations.
Full-spectrum LEDs work for both stages. Some growers use blue-heavy light for veg and red-heavy for flower. Dual-spectrum or adjustable LEDs handle both stages without swapping.
A 300W LED running 18 hours/day costs about $1.50–$2/day at average electricity rates. Use our Electricity Usage Cost Calculator for your exact rate.
LEDs are 40–60% more energy efficient, produce less heat (less cooling needed), last 50,000+ hours vs 10,000 for HPS, and offer full spectrum. HPS is cheaper upfront but costs more to operate.
Yes, completely free. Calculate coverage for any grow space and light wattage instantly.